Near-room-temperature water-mediated densification of bulk van der Waals materials from their nanosheets.

The conventional fabrication of bulk van der Waals (vdW) materials requires a temperature above 1,000 °C to sinter from the corresponding particulates. Here we report the near-room-temperature densification (for example, ∼45 °C for 10 min) of two-dimensional nanosheets to form strong bulk materials with a porosity of <0.1%, which are mechanically stronger than the conventionally made ones. The mechanistic study shows that the water-mediated activation of van der Waals interactions accounts for the strong and dense bulk materials. Initially, water adsorbed on two-dimensional nanosheets lubricates and promotes alignment. The subsequent extrusion closes the gaps between the aligned nanosheets and densifies them into strong bulk materials. Water extrusion also generates stresses that increase with moulding temperature, and too high a temperature causes intersheet misalignment; therefore, a near-room-temperature moulding process is favoured. This technique provides an energy-efficient alternative to design a wide range of dense bulk van der Waals materials with tailored compositions and properties.

Ginseng-DF ameliorates intestinal mucosal barrier injury and enhances immunity in immunosuppressed mice by regulating MAPK/NF-κB signaling pathways.

PURPOSE: Dietary fiber (DF) has a good application prospect in effectively restoring the integrity of the intestinal mucosal barrier. Ginseng-DF has good physicochemical properties and physiological activity and shows positive effects in enhancing immunity. The aim of this study was to investigate the protective effect of Ginseng-DF on intestinal mucosal barrier injury induced by cyclophosphamide (CTX) in immunosuppressed mice and its possible mechanism. METHODS: The effects of Gginseng-DF on immune function in mice were studied by delayed-type hypersensitivy, lymphocyte proliferation assay and NK cytotoxicity assay, the T lymphocyte differentiation and intestinal barrier integrity were analyzed by flow cytometry and western blot. RESULTS: Ginseng-DF (2.5% and 5%) could attenuate the inhibition of DTH response by CTX, promote the transformation and proliferation of lymphocytes, and stimulate NK effector cell activity. At the same time, Ginseng-DF could restore the proportion of CD4+/CD8+ T lymphocytes induced by CTX to different extents, improved spleen tissue damage, promoted the secretion of immunoglobulin IgG, and enhanced body immunity. More importantly, Ginseng-DF could up-regulate the contents of TNF-α, IFN-γ, IL-6 and IL-1ß in serum and intestine of immunosuppressed mice to maintain the balance between Th1/Th2 cytokines, and improve the permeability of intestinal mucosal barrier. Meanwhile, Ginseng-DF could reduce intestinal epithelial cell apoptosis and improve intestinal adaptive immunity in CTX-induced immunosuppressed mice by regulating MAPK/NF-κB signaling pathway. CONCLUSION: Ginseng-DF can be used as a safe dietary supplement to enhance body immunity and reduce intestinal mucosal injury caused by CTX.

Construction of the Fast Potassiation Path in Sbx Bi1-x @NC Anode with Ultrahigh Cycling Stability for Potassium-Ion Batteries.

Due to the scarce of lithium resources, potassium-ion batteries (PIBs) have attracted extensive attention due to their similar electrochemical properties to lithium-ion batteries (LIBs) and more abundant potassium resources. Even though there is considerable progress in SbBi alloy anode for LIBs and PIBs, most studies are focused on the morphology/structure tuning, while the inherent physical features of alloy composition's effect on the electrochemical performance are rarely investigated. Herein, combined the nanonization, carbon compounding, and alloying with composition regulation, the anode of nitrogen-doped carbon-coated Sbx Bi1-x (Sbx Bi1-x @NC) with a series of tuned chemical compositions is designed as an ideal model. The density functional theory (DFT) calculation and experimental investigation results show that the K+ diffusion barrier is lower and the path is easier to carry out when element Bi dominates the potassiation reaction, which is also the reason for better circulation. The optimized Sb0.25 Bi0.75 @NC shows an excellent cycling performance with a reversible specific capacity of 301.9 mA h g-1 after 500 cycles at 0.1 A g-1 . Meanwhile, the charge-discharge mechanism is intuitively invetigated and analyzed by in situ X-ray diffraction (XRD) and transmission electron microscopy (TEM) in detail. Such an alloy-type anode synthesis approach and in situ observation method provide an adjustable strategy for the designing and investigating of PIB anodes.

Eutectic-Based Polymer Electrolyte with the Enhanced Lithium Salt Dissociation for High-Performance Lithium Metal Batteries.

The deployment of lithium metal anode in solid-state batteries with polymer electrolytes has been recognized as a promising approach to achieving high-energy-density technologies. However, the practical application of the polymer electrolytes is currently constrained by various challenges, including low ionic conductivity, inadequate electrochemical window, and poor interface stability. To address these issues, a novel eutectic-based polymer electrolyte consisting of succinonitrile (SN) and poly (ethylene glycol) methyl ether acrylate (PEGMEA) is developed. The research results demonstrate that the interactions between SN and PEGMEA promote the dissociation of the lithium difluoro(oxalato) borate (LiDFOB) salt and increase the concentration of free Li+ . The well-designed eutectic-based PAN1.2 -SPE (PEGMEA: SN=1: 1.2 mass ratio) exhibits high ionic conductivity of 1.30 mS cm-1 at 30 °C and superior interface stability with Li anode. The Li/Li symmetric cell based on PAN1.2 -SPE enables long-term plating/stripping at 0.3 and 0.5 mA cm-2 , and the Li/LiFePO4 cell achieves superior long-term cycling stability (capacity retention of 80.3 % after 1500 cycles). Moreover, Li/LiFePO4 and Li/LiNi0.6 Co0.2 Mn0.2 O2 pouch cells employing PAN1.2 -SPE demonstrate excellent cycling and safety characteristics. This study presents a new pathway for designing high-performance polymer electrolytes and promotes the practical application of high-stable lithium metal batteries.

In-Situ Synthesis of Carbon-Encapsulated Atomic Cobalt as Highly Efficient Polysulfide Electrocatalysts for Highly Stable Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries have been considered as one of the most promising electrochemical energy storage systems because of their high energy density. However, a series of issues severely limit the practical performances of Li-S batteries such as low conductivity, significant volume change, and shuttle effect. The hollow carbon spheres with huge voids and high electrical conductivity are promising as sulfur hosts. Unfortunately, the nonpolar nature of carbon materials cannot prevent the shuttle effect effectively. In this case, the atomic cobalt is introduced to a nitrogen-doped hollow carbon sphere (ACo@HCS) through polymerization and controlled pyrolysis. The atomic cobalt dopants not only act as active sites to restrict the shuttle effect, but also can promote the kinetics of the sulfur redox reactions. ACo@HCS acting as sulfur host exhibits a high discharge capacity (1003 mAh g-1 ) at a 1.0 C rate after 500 cycles, and the corresponding decay rate is as low as 0.002% per cycle. This exciting work paves a new way to design high-performance Li-S batteries.

Multifunctional Metal Phosphides as Superior Host Materials for Advanced Lithium-Sulfur Batteries.

For the past few years, a new generation of energy storage systems with large theoretical specific capacity has been urgently needed because of the rapid development of society. Lithium-sulfur (Li-S) batteries are regarded as one of the most promising candidates for novel battery systems, since their resurgence at the end of the 20th century Li-S batteries have attracted ever more attention, attributed to their notably high theoretical energy density of 2600 W h kg-1 , which is almost five times larger than that of commercial lithium-ion batteries (LIBs). One of the determining factors in Li-S batteries is how to design/prepare the sulfur cathode. For the sulfur host, the major technical challenge is avoiding the shuttling effect that is caused by soluble polysulfides during the reaction. In past decades, though the sulfur cathode has developed greatly, there are still some enormous challenges to be conquered, such as low utilization of S, rapid decay of capacity, and poor cycle life. This article spotlights the recent progress and foremost findings in improving the performance of Li-S batteries by employing multifunctional metal phosphides as host materials. The current state of development of the sulfur electrode of Li-S batteries is summarized by emphasizing the relationship between the essential properties of metal phosphide-based hybrid nanomaterials, the chemical reaction with lithium polysulfides and the latter's influence on electrochemical performance. Finally, trends in the development and practical application of Li-S batteries are also pointed out.

Cathodes for Aqueous Zn-Ion Batteries: Materials, Mechanisms, and Kinetics.

As concerns about the safety of lithium-ions batteries (LIBs) increases, aqueous zinc-ion batteries (ZIBs) with a lower cost, higher safety, and higher co-efficiency have attracted more and more interest. However, finding suitable cathode materials is still an urgent problem in ZIBs. In recent years, a lot of significant works have been reported, including manganese-based cathodes, vanadium-based cathodes, Prussian blue analog-based materials, and sustainable quinone cathodes. In this review, some typical cathode materials are introduced. The detailed storage mechanisms and methods for improving the reaction kinetics of the zinc ions are summarized. Finally, the issues, challenges, and the research directions are provided.

Iron toxicity-induced regulation of key secondary metabolic processes associated with the quality and resistance of Panax ginseng and Panax quinquefolius.

Panax ginseng and Panax quinquefolius can survive for long periods of time in iron toxicity-stressed environments, which cause rusty roots and reduced productivity. To reveal the proteomic changes in these two Panax species in response to iron toxicity stress, plants of these two species were divided into a control group and an iron toxicity-stress group. An isobaric tags for relative and absolute quantitation (iTRAQ) proteomics approach was used to explore the changes in protein accumulation and the potential mechanisms underlying the response to iron toxicity stress in the two Panax species. Proteomic analyses revealed approximately 725 differentially expressed proteins (DEPs) in the iron toxicity-stress and control groups, including 233 and 492 proteins whose expression was upregulated and downregulated, respectively. The expression of DEPs related to photosynthesis was significantly downregulated, and DEPs whose expression was significantly upregulated were associated with redox reactions. Many upregulated DEPs were also involved in pathways such as those involving phenylpropanoid, flavonoid, isoflavone and ginsenoside synthesis. The abundance of some ginsenoside monomers (Rg1 and Rb3) also significantly increased in P. ginseng and P. quinquefolius. Moreover, P. quinquefolius contained 455 DEPs whose expression was higher than that in P. ginseng, including many proteins related to the regulation of ion homeostasis, indicating that P. quinquefolius is more resistant to iron toxicity stress than P. ginseng is.

Occurrence of postharvest snow rot caused by Sclerotinia nivalis on Asian ginseng in China.

Asian ginseng (Panax ginseng) is a valuable medicinal plant that is commercially cultivated in China. A long postharvest storage period is required before ginseng is processed. From October 2019 to May 2020, snow rot was observed on the roots of 4- and 5-year-old fresh ginseng stored in three cold storage facilities located in Tonghua and Changbai cities in northeastern China, which are the most important regions for Asian ginseng production. We sampled 1,000 ginseng roots from the three cold storage facilities, and the average disease incidence was 21%. Initially, sparse hyphae and microsclerotia appeared on the root epidermis. Lesions gradually softened and the epidermis detached easily. Multiple infected sites slowly converged, resulting in the formation of a dense complex of multiple sclerotia and thick hyphae on the surface of the ginseng root as well as internal decay. The infection eventually spread to the adjacent ginseng roots (Fig. 1). Sixteen diseased ginseng roots were collected and then sclerotia were removed from the root surface, immersed in 1% NaClO for 2 min, rinsed three times with sterile water, and placed on potato dextrose agar (PDA) containing streptomycin (40 µg/mL) in Petri dishes. After a 3-day incubation at 20 °C in darkness, 22 suspected Sclerotinia isolates were obtained. Isolates SN1 and SN2 were randomly selected for identification. On PDA, fast-growing colonies produced white, sparse, powdery, and cotton-like aerial mycelia, and the reverse side showed the same color (Fig. 2). Small and white sclerotial primordia formed 3 days later and a ring of sclerotia was detected at the plate periphery. At 7 to 10 days after incubation, the mature sclerotia were black, spherical-to-subspherical, and elongated or fused to form irregular shapes. Each Petri dish produced 55-65 sclerotia, measuring 1.1 × 1.2 to 3.2 × 3.9 mm (n = 100). The sclerotia were firmly attached to the agar surface. The isolates were initially identified as Sclerotinia sp. (Saito 1997). After sequencing the nuclear ribosomal internal transcribed spacer region (MW927134 and MW927135) and the ß-tubulin gene (MW929179 and MW929180) (White et al. 1990; Glass and Donaldson 1995), BLAST searches revealed 100% homology with JX262268 and JX296007 of the published S. nivalis strain KGC-S0601, respectively. The pathogenicity of the two isolates was tested using detached ginseng roots. Briefly, healthy roots were washed, surface-disinfested with 75% alcohol, and rinsed with sterile water. Mycelial plugs (5 mm diameter) removed from the margin of actively growing colonies on PDA were placed on the ginseng roots. For each isolate, four roots were inoculated, with two plugs per root. Additionally, PDA plugs without mycelia were used as the negative control. The roots were placed in a fresh-keeping box at 20 °C in darkness and evaluated after 7 days. The pathogenicity test was repeated twice. The symptoms on the inoculated roots were the same as those observed on the roots during cold storage, whereas the control roots remained symptomless. The same fungus was reisolated consistently from all infected roots and its identity was confirmed by resequencing, thereby fulfilling Koch's postulates. To the best of our knowledge, this is the first report of S. nivalis causing postharvest snow rot on Asian ginseng in China. The occurrence of this disease threatens the postharvest storage of Asian ginseng. Hence, effective management strategies must be developed.

[Progress of studies on ATP-binding cassette transporters and transportation of secondary metabolites in medicinal plants].

ATP-binding cassette(ABC) transporters are one of the largest protein families in organisms, with important effects in regulating plant growth and development, root morphology, transportation of secondary metabolites and resistance of stress. Environmental stress promotes the biosynthesis and accumulation of secondary metabolites, which determines the quality of medicinal plants. Therefore, how to improve the accumulation of secondary metabolites has been a hotspot in studying medicinal plants. Many studies have showed that ABC transporters are extremely related to the transportation and accumulation of secondary metabolites in plants. Recently, with the great development of genomics and transcriptomic sequencing technology, the regulatory mechanisms of ABC transporters on secondary metabolites have attached great attentions in medicinal plants. This paper reviewed the mechanisms of different groups of ABC transporters in transporting secondary metabolites through cell membranes. This paper provided key theoretical basis and technical supports in studying the mechanisms of ABC transporters in medicinal plant, and promoting the accumulation of secondary metabolites, in order to improve the quality of medicinal plants.

Ultralow Volume Change of P2-Type Layered Oxide Cathode for Na-Ion Batteries with Controlled Phase Transition by Regulating Distribution of Na.

Most P2-type layered oxides exhibit a large volume change when they are charged into high voltage, and it further leads to bad structural stability. In fact, high voltage is not the reason which causes the irreversible phase transition. There are two internal factors which affect structural evolution: the amount and distribution of Na ions retained in the lattice. Hereon, a series of layered oxides Na2/3 Mnx Nix-1/3 Co4/3-2x O2 (1/3≤x≤2/3) were synthesized. It is observed that different components have different structural evolutions during the charge/discharge processes, and further researches find that the distribution of Na ions in layers is the main factor. By controlling the distribution of Na ions, the phase transition process can be well controlled. As the referential component, P2-Na2/3 Mn1/2 Ni1/6 Co1/3 O2 cathode with uniform distribution of Na ions is cycled at the voltage window of 1.5-4.5 V, which exhibits a volume change as low as 1.9 %. Such a low strain is beneficial for cycling stability. The current work provides a new and effective route to regulate the structural evolution of the promising P2-type layered cathode for sodium ion batteries.

B,N Codoped Graphitic Nanotubes Loaded with Co Nanoparticles as Superior Sulfur Host for Advanced Li-S Batteries.

Lithium-sulfur batteries (LSBs) are considered as one of the best candidates for novel rechargeable batteries due to their high energy densities and abundant required materials. However, the poor conductivity and large volume expansion of sulfur and the "shuttle effect" of lithium polysulfides (LPSs) have significantly hindered the development and successful commercialization of LSBs. Bean-like B,N codoped carbon nanotubes loaded with Co nanoparticles (Co@BNTs), which can act as advanced sulfur hosts for the novel LSB cathode, are fabricated. Uniform graphitic nanotubes improve the conductivity of the electrode and load more electroactive sulfur and buffer volume expansion during the electrochemical reaction. In addition, loaded Co nanoparticles and codoped B,N sites can significantly suppress the "shuttle effect" of LPSs with strong chemical interaction. It is established that the Co nanoparticles and codoped B,N can provide more active sites to catalyze the redox reaction of sulfur cathode. This stable Co@BNTs-S cathode displays an exceptional electrochemical performance (1160 mA h g-1 after 200 cycles at 0.1 C) and outstanding stable cycle performance (1008 mA h g-1 after 400 cycles at 1.0 C with an extremely low attenuation rate of 0.038% per cycle).

Recent Progress of P2-Type Layered Transition-Metal Oxide Cathodes for Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) have attracted much attention due to their abundance, easy accessibility, and low cost. All of these advantages make them potential candidates for large-scale energy storage. The P2-type layered transition-metal oxides (Nax TMO2 ; TM=Mn, Co, Ni, Ti, Fe, V, Cr, and a mixture of multiple elements) exhibit good Na+ ion conductivity and structural stability, which make them an excellent choice for the cathode materials of SIBs. Herein, the structural evolution, anionic redox reaction, some challenges, and recent progress of Nax TMO2 cathodes for SIBs are reviewed and summarized. Moreover, a detailed understanding of the relationship of chemical components, structures, phase compositions, and electrochemical performance is presented. This Review aims to provide a reference for the development of P2-type layered transition-metal oxide cathode materials for SIBs.

Recent Progress in Organic-Inorganic Composite Solid Electrolytes for All-Solid-State Lithium Batteries.

Conventional lithium-ion batteries, with flammable organic liquid electrolytes, have serious safety problems, which greatly limit their application. All-solid-state batteries (ASSBs) have received extensive attention from large-scale energy-storage fields, such as electric vehicles (EVs) and intelligent power grids, due to their benefits in safety, energy density, and thermostability. As the key component of ASSBs, solid electrolytes determine the properties of ASSBs. In past decades, various kinds of solid electrolytes, such as polymers and inorganic electrolytes, have been explored. Among these candidates, organic-inorganic composite solid electrolytes (CSEs) that integrate the advantages of these two different electrolytes have been regarded as promising electrolytes for high-performance ASSBs, and extensive studies have been carried out. Herein, recent progress in organic-inorganic CSEs is summarized in terms of the inorganic component, electrochemical performance, effects of the inorganic ceramic nanostructure, and ionic conducting mechanism. Finally, the main challenges and perspectives of organic-inorganic CSEs are highlighted for future development.

Silicon application and related changes in soil bacterial community dynamics reduced ginseng black spot incidence in Panax ginseng in a short-term study.

BACKGROUND: This study analyzed the effect of silicon (Si) application on the occurrence of ginseng black spot caused by Alternaria panax. We explored the differences in soil physical and chemical factors and microbial community structure following Si application as well as the key factors that affected the occurrence of ginseng black spot in soil. Potted Panax ginseng plants were used to assess the effect of Si treatment on ginseng black spot. Soil physical and chemical properties were comprehensively analyzed. Bacterial communities were analyzed using Illumina HiSeq sequencing targeting the 16S rRNA gene. RESULTS: After inoculation with A. panax, the morbidity (and morbidity index) of ginseng with and without Si was 52% (46) and 83% (77), respectively. Soil physical and chemical analysis showed that under the ginseng black spot inoculation, bacterial communities were mainly affected by pH and available potassium, followed by ammonium nitrogen and available Si. NMDS and PLS-DA analyses and the heat maps of relative abundance revealed that Si application elevated the resistance of ginseng black spot as regulated by the abundance and diversity of bacterial flora in rhizosphere soils. Heatmap analysis at the genus level revealed that A. panax + Si inoculations significantly increased the soil community abundance of Sandaracinus, Polycyclovorans, Hirschia, Haliangium, Nitrospira, Saccharothrix, Aeromicrobium, Luteimonas, and Rubellimicrobium and led to a bacterial community structure with relative abundances that were significantly similar to that of untreated soil. CONCLUSIONS: Short-term Si application also significantly regulated the structural impact on soil microorganisms caused by ginseng black spot. Our findings indicated that Si applications may possibly be used in the prevention and treatment of ginseng black spot.

Dramatically Enhanced Li-Ion Storage of ZnO@C Anodes through TiO2 Homogeneous Hybridization.

Amorphous nanoparticles of ZnO and TiO2 embedded in carbon nanocages (AZT⊂CNCs) were successfully synthesized through a simple annealing process of TiO2 -coated zeolitic imidazolate framework-8 (ZIF-8). In the current anode of AZT⊂CNCs, tiny ZnO and TiO2 nanoparticles were uniformly distributed in the carbon matrix (carbon nanocages), which could effectively buffer the volume expansion of electroactive ZnO and provide excellent electric conductivity. After fully investigating the electrochemical performance of the AZT⊂CNCs samples obtained with different additive amounts of tetrabutyl orthotitanate (TBOT) for TiO2 coating, it has been found that AZT-30 (0.1 g ZIF-8 with 30 mL TBOT) shows the best cycle stability (510 mA h g-1 after 350 cycles at 200 mA g-1 ) and a superior rate capability (610 mA h g-1 after 3500 cycles at 2 A g-1 ). The greatly enhanced Li-ion storage performance could be ascribed to the fact that the introduction of amorphous TiO2 could activate the reversible lithiation/delithiation reaction of ZnO during the charge/discharge process.

Facile Synthesis of Peapod-Like Cu3 Ge/Ge@C as a High-Capacity and Long-Life Anode for Li-Ion Batteries.

As anode materials for high-performance Li-ion batteries, peapod-like Ge-based composites, including Ge, a Li-inactive conducting Cu3 Ge, and a porous carbon matrix are synthesized simply by annealing CuGeO3 @dopamine in a H2 /Ar atmosphere. The introduction of the carbon layer and inactive alloying phase Cu3 Ge not only enhances the electrical conductivity of the Ge anode, but also reduces the volume change of Ge during the cell cycle as a buffer. In particular, the anode of this peapod-like Cu3 Ge/Ge@C shows an excellent long cycle life as well as outstanding capacity performance, with a discharge specific capacity up to 934 mA h g-1 after 500 cycles.

Effects of different substrates on low-temperature storage of fresh ginseng.

BACKGROUND: Fresh ginseng was buried in three types of sand with different moisture contents and three types of soil and then stored at 2 °C to determine the effects of these storage substrates on fresh ginseng. RESULTS: At a storage time of 200 days, ginseng stored in underforest soil softened the most slowly and had a significantly greater firmness compared to the other samples (P < 0.05). The amount of most ginsenosides changed after storage for most of the substrates. Samples stored in ginseng soil and biological fertilizer had the highest concentration of total saponin and ginseng polysaccharides, respectively. Fresh ginseng stored in medium-water content sand had a significantly lower polyphenol oxidase activity (P < 0.05). A significant difference was observed in the total concentration of nucleosides and nucleobases between the ginseng samples stored with and without substrates (P < 0.05). CONCLUSION: The data obtained in the present study suggest that the use of storage substrates is an optimal method for extending the shelf life of fresh ginseng without detrimental effects on its components. © 2019 Society of Chemical Industry.

FeP@C Nanotube Arrays Grown on Carbon Fabric as a Low Potential and Freestanding Anode for High-Performance Li-Ion Batteries.

An anode of self-supported FeP@C nanotube arrays on carbon fabric (CF) is successfully fabricated via a facile template-based deposition and phosphorization route: first, well-aligned FeOOH nanotube arrays are simply obtained via a solution deposition and in situ etching route with hydrothermally crystallized (Co,Ni)(CO3 )0.5 OH nanowire arrays as the template; subsequently, these uniform FeOOH nanotube arrays are transformed into robust carbon-coated Fe3 O4 (Fe3 O4 @C) nanotube arrays via glucose adsorption and annealing treatments; and finally FeP@C nanotube arrays on CF are achieved through the facile phosphorization of the oxide-based arrays. As an anode for lithium-ion batteries (LIBs), these FeP@C nanotube arrays exhibit superior rate capability (reversible capacities of 945, 871, 815, 762, 717, and 657 mA h g-1 at 0.1, 0.2, 0.4, 0.8, 1.3, and 2.2 A g-1 , respectively, corresponding to area specific capacities of 1.73, 1.59, 1.49, 1.39, 1.31, 1.20 mA h cm-2 at 0.18, 0.37, 0.732, 1.46, 2.38, and 4.03 mA cm-2 , respectively) and a stable long-cycling performance (a high specific capacity of 718 mA h g-1 after 670 cycles at 0.5 A g-1 , corresponding to an area capacity of 1.31 mA h cm-2 at 0.92 mA cm-2 ).

Nanoconfined Oxidation Synthesis of N-Doped Carbon Hollow Spheres and MnO2 Encapsulated Sulfur Cathode for Superior Li-S Batteries.

The sulfur cathode, as a new generation of lithium-ion battery cathode material, has a high theoretical energy density of about 2500 Wh kg-1 . However, the low conductivity of sulfur and the "shuttle effect", widely presenting in the lithiation/de-lithiation process, seriously hinder its practical application. Here, we report a new nanoconfined oxidation route (first complete oxidation of metal sulfide and subsequently partial oxidation of the generated S from sulfide) for S cathode encapsulated with MnO2 nanosheets and N-doped carbon hollow spheres. This nanoconfined oxidation route can successfully confine the sulfur particles in the interior of the carbon shell, and the rationally introduced nonpolar carbon and polar MnO2 can both reduce the dissolution of polysulfide during the charge-discharge process. The obtained well-defined S-MnO2 @C cathode exhibits high specific capacity with excellent cycling performance and superior rate capability.